The use of thin film mirrors in large types of visual display apparatus is well known. Thus, for example, it is well known to use thin film mirrors of a concave near-spherical form in collimated displays for use in simulators. The simulators may be used for a wide variety of purposes including training (e.g., flight simulators), research, leisure and entertainment.
The thin film mirrors are usually constructed by fixing a film across an open face of an otherwise enclosed chamber. The edges of the chamber to which the film is attached lie on the surface of the desired mirror shape. In the case of simulator display apparatus, the mirror is usually part of a sphere which is bounded at its top and bottom by lines of latitude. Left and right hand ends of the mirror chamber may be lines of longitude or more complicated arrangements.
Standard methods of for making such mirrors involve lightly tensioning the film as it is applied such that it forms part of the frustum of a cone. The vacuum chamber is then partially evacuated, and the greater external air pressure forces the film into the desired mirror shape. The accuracy of the mirror shape may affect the quality of an image provided by the display apparatus utilizing the mirror. Various factors may affect the final shape of the mirror, including the characteristics of the chamber edges, the means by which the film is attached to the chamber edges, and manner in which the film stretches as the chamber is evacuated.
The present invention is directed to systems and methods for making improved film mirrors.